Right, so long as there isn't mutation, we're golden, which is why the machine code is the same.
This is, after all, why Godbolt was first invented as I suspect you know (Matt Godbolt wondered if C++ iterators really do produce the same machine code as a hand-rolled C-style for loop, and rather than just trust an expert he built the earliest Compiler Explorer to show that yes, with real C++ code you get the same machine code, any time spent hand-rolling such loops is time wasted)
I don't understand what you mean by "domains where C++ is unavoidable" in this context. C++ is a choice, presumably usually a reasonable choice, but a choice, so if they wanted to people could avoid it.
Memory tagging (which is what MTE is about) reminds me of ASLR and password entropy requirements. They're slightly raising the bar which is not something I have much time for. I prefer to put the effort in to solve problems permanently so I can worry about something else instead. Whether that's a practical opportunity here is unclear though, and I think Rust is a big part of finding out.
